OK
1996 silverado 5.7 vortec car slowly accelerates without pressing gas, also code misfire #4 cylinder code p0304. When I start the truck it idles high for a few seconds then settles down to around 800. Truck drives with a lot of power and occasional high idling. Also when truck auto trans. switches to 2nd gear the truck kinda bucks. Already changed air filter, cleaned Mass air flow sensor, changed oil, replaced idle air control sensor, cleaned throttle body,new spark plugs gapped. Old Spark plug on #4 Cylinder was corroded with white deposits. new cap and dist cover. I love this truck but dam WTH?

 

Most of the stuff you replaced has nothing to do with a cylinder #4 misfire. One thing I don't see on your shopping list is plug wires, I would check into that next. With a misfire, cylinder #4 would be running rich. The 02 sensor on that bank will adjust the air/fuel mix to try and compensate for the rich condition, which can affect your idle, engine performance, and gas mileage.

 

Mechanic says injectors working, fine but he says its the valves on cylinder #4
for the most part im a diy. Is a valve job hard to do? I have a Hayes repair manual. Mechanic wants to charge me $500!!!!!